University-Developed Process will Repurpose Old Technology into Tiles

Malabika Chaudhuri, a scientist in the Vitreous State Laboratory, examines ceramic tiles made with CRT glass.

Formerly the centerpieces of living rooms and offices, old TVs and computer monitors can become a threat to the environment when improperly disposed of. The bulky screens are made with cathode ray tubes (CRTs) that include thick lead glass to block X-ray emissions.

Because the screens can leach toxic substances when disposed of, the Environmental Protection Agency ruled in 2001 that CRTs must be brought to special recycling facilities where smelters are used to remove the lead. Since the facilities are both rare and expensive, hundreds of millions of pounds of CRT screens have been stockpiled around the country with nowhere to go.

Hoping to solve that problem is Ian Pegg, physics professor and director of the Vitreous State Laboratory (VSL) at The Catholic University of America. Nearly 10 years ago, Pegg was contracted by a group of entrepreneurs in Wisconsin to find an alternative recycling solution for CRTs. Together with VSL scientists Hao Gan and Malabika Chaudhuri, Pegg developed a method for repurposing CRT glass into ceramic floor tiles.

To make tiles, the CRT glass is crushed into a fine powder and mixed with other ingredients like clay and binders. The mixture is then pressed into molds and baked for several hours. The end result is a tile that is very dense and durable with low water absorption.

For Pegg, the idea to repurpose CRT glass as ceramic tiles was not a big stretch of the imagination.
“We know about the glass-making processes and ceramic-making processes, and inventions are often just making connections,” he said. “If you’re aware of the things to connect, then it’s easy.”

What was surprising was how much the presence of CRT glass improved the tiles. The same lead that makes CRT glass potentially toxic makes tiles extra strong and durable. Because the tile is already 70 percent glass, it can be colored from within and there is no need for a glaze.

The new method also saves energy since tiles made with CRT glass require less time in the kiln and can be cooked at a lower temperature. While cooking, the tile maintains its shape and sharp edges.

“It actually turns out that the glass is very useful in this tile-making process,” Pegg said. “Seventy percent of what you’re using is a waste material so you’re disposing of a waste, you’ve got raw materials for free essentially, and you’ve got lower energy costs because of the lower temperature and the quicker firing process.”

The technology is patent-pending and licensed to DP Electronic Recycling in Elkhorn, Wis., which is taking steps to test the process with the Environmental Protection Agency and the state Board of Natural Resources. According to the Milwaukee Business Journal, once approval is received, the company hopes to begin manufacturing the tiles within the next few years. When that begins to happen, Catholic University could receive royalties.

“It would be very nice if they can get something up and running, dealing with an environmental problem that needs a solution,” Pegg said. “That would be very satisfying. And to see some money coming back to the University, that would be even better.”

Catholic University’s Vitreous State Laboratory (VSL) is a leading research center for the studies of materials in their vitreous — or glass — state. At VSL, 100 Ph.D. scientists and engineers develop applications in such areas as nuclear environmental protection, fiber optics, biophysics, and nanotechnology. Established in 1968, VSL operates on grants and private contracts totaling on average $7 million a year.